Reports confirm that players who have the PlayStation Plus Collection are required to follow a step first before getting this particular access.
According to media outlet Gamespot, they have made some tests and can confirm that players can play the games in the PS Plus Collection on the PlayStation 4, but there is a requirement. They must first redeem the games they want to play on the next-gen console PS5. There is no need to install it there since what they all need is confirmation that the games have been redeemed.
After redeeming the titles, use the same PlayStation account they used to redeem the games and then download them on the PS4. No more action is needed after that.
Some are suggesting that players can just ask their friends with PS5 to log in their accounts there and redeem their PS Plus Collection titles. After that they can just log in their PS4s and download there. No one has reported that this has worked, but tell us if it does. That is a good workaround for those who do not have plans to buy a PS5 this year.
Source: Gamespot